The invention herein resides in the art of currency validators or note acceptors, and particularly to such devices known as slot acceptors. Specifically, the invention relates to a detector for determining the presence of foreign objects such as a retrieving string or the like within the note path of the note acceptor following the time that the end of the note has cleared the validator sensors in the note path.
The use of currency validators or note acceptors for purposes of authenticating currency and providing goods, services or change in return therefor is extensively known. Prominent among the note acceptors are those termed as xe2x80x9cslotxe2x80x9d acceptors, having a slot opening in the housing of the note acceptor for receiving tendered currency. The slot communicates with a note path through which the currency is transported and tested for authenticity. At the end of the note path, the currency is either returned by reversal of the transport system in the event that the currency is determined to be invalid, or the currency is escrowed for subsequent vending and acceptance, in the event it is authenticated.
Those who would seek to defeat slot acceptors have devised various methods for retrieving the currency from the escrowed position. In this manner, the vended goods, services and/or change is enjoyed, while the tendered currency is maintained by the unscrupulous individual. Common among such attempts of retrieval is the implementation of strings or tape secured at one end to the currency and maintained at the other by the individual. Once the bill has been validated and passed to escrow, and a xe2x80x9cvendxe2x80x9d signal has been emitted by the validator, the currency is then retrieved by means of the string or tape.
In the past, various methods have been employed for defeating such stringing techniques. Among these known devices are rotating slotted drums, sharp tooth gates, rear clear pawls, and the like. While these prior art techniques have been generally successful, they inherently disable the note acceptor upon implementation and thereby place the note acceptor in a xe2x80x9cdownxe2x80x9d state until service personnel access the equipment, remove the tape or string, and clear the system for reactivation.
While optical sensors of sorts have been considered in the past, they have typically been incapable of monitoring the presence of fine material such as cellophane tape, thread, and monofilament string such as fishing line and the like. Moreover, optical systems which have previously been considered have not been of an adaptive nature, but have been given to adverse effects of aging, thermal drift, and the like.
There is a need in the art for a highly sensitive adaptive string detector for use in currency validators which is constantly adjusted to maintain a high degree of resolution and accuracy and which is capable of optically detecting otherwise undetectable retrieving means such as those mentioned above.
In light of the foregoing, it is a first aspect of the invention to provide an adaptable string detector for currency validators having a sensitivity which is continually adjusted to compensate for any effects of aging, thermal drift, and the like.
Another aspect of the invention is the provision of an adjustable string detector for currency validators which provides for a fixed optical window of acceptability across the note path.
Yet a further aspect of the invention is the provision of an adaptable string detector for currency validators which can defeat stringing efforts without disabling the validator itself.
Yet a further aspect of the invention is the provision of an adaptable string detector for currency validators which is electronic in nature, not given to problems incident to mechanical structures employed for the same purpose.
Still a further aspect of the invention is the provision of an adaptable string detector for currency validators which is conducive to implementation with state of the art slot detectors employing microprocessor controls.
The foregoing and other aspects of the invention which will become apparent as the detailed description proceeds are achieved by an antistringing control system for currency validators, comprising: a note path having an opening for receiving inserted notes; a light source on a first side of said note path adjacent to said opening; a light detector on a second side of said note path adjacent to said opening, said light detector being positioned to receive light from said light source traversing said note path and emitting a first signal corresponding to the amount of light so received; and a comparator receiving said first signal and emitting a second signal indicative of any presence of a foreign element within said note path and between said light source and light detector.
Other aspects of the invention are attained by a method for determining the presence of any foreign material in the note path of a currency validator, following a determination of the validity of a note tendered in the path, comprising: casting a light across the note path; sensing the amount of light traversing the note path from that cast across the note path; generating a signal corresponding to said amount of light sensed; and comparing said signal to a first threshold indicative of the absence of foreign material within the note path; and ejecting the note from the note path upon said comparison of said signal with said first threshold indicating the presence of foreign material within the note path.
Still further aspects of the invention are attained by an antistringing control system for a currency validator, comprising: a note path; a light source and a light sensor juxtaposed on opposite sides of said note path, said light sensor generating a first signal corresponding to light received thereby from said light source; a window comparator connected to said light sensor and receiving said first signal, said window comparator having a characteristic window associated therewith and generating a second signal when said first signal falls outside of said window; and a controller connected to said window comparator and receiving said second signal, said control rejecting any note tendered to the currency validator upon receipt of said second signal.